leetcode 167. 两数之和 II - 输入有序数组

答案一：用例全部通过，但是超时。朴实的两层循环

class Solution {
public:vector<int> twoSum(vector<int>& numbers, int target) {vector<int> result;for (int i = 0; i < numbers.size(); i++) {int ans = target - numbers[i];int j = 0;for (j = i+1; (j < numbers.size()) && (numbers[j] < ans); j++){;}if ((j < numbers.size()) && (numbers[j] == ans)) {result.push_back(i+1);result.push_back(j+1);break;}}return result;}
};

答案二：双指针：头、尾指针

class Solution {
public:vector<int> twoSum(vector<int>& numbers, int target) {vector<int> result;int left = 0, right = numbers.size()-1;while(left < numbers.size() && right >= 0 && left <= right) {int sum = numbers[left] + numbers[right];while(sum < target && left < numbers.size()) {left++;sum = numbers[left] + numbers[right];} while(sum > target && right >= 0) {right--;sum = numbers[left] + numbers[right];}if (sum == target) {result.push_back(left+1);result.push_back(right+1);break;}}return result;}
};